Radiant Barrier Insulation?

I saw some of it at the local Mueller's (tin roofing/metal buildings) dealer a couple months ago. Salesman demonstrated it with a heatlamp and thermometer...something like 180 on one side (with the light) and 75 on the other side.

Got me to wondering whether I should use fiberglass or foam insulation in my 'dream home' roof, or use the radiant barrier material. Would be nice if someone has actually used it. Condensation problems? Need to know more before I insulate the vaulted ceilings with it.

 

I just bought 10 rolls of the stuff. Its unclear just how good it is. It is not the same as regular insulation. Alledgedly, over 90% of heat loss from a structure is radiant. Normal insulation does not stop radiant loss.

I started installing it on the ceiling of my garage. Its a pain working in the rafters, but it is a lot better than installing fiberglass. I was going to buy it on ebay. I bought it at home depot instead. The products were slightly different, but the price/sq ft was the same and the ebay guy wanted $26 per roll to ups it to me. Duh.

The ebay guy wrote me that if I installed it parallel to the roof that the r value increases with each inch of air space between the roof and foil up to 6". After 6" the r value falls quickly. The maximum r value at this spacing was reportedly r-39. I don't really believe it. BUT, I'm sold anyway.

The stuff home depot sells is labeled as "Reflectix." Its the only radiant barrier product home depot carries. They have a website, but its nothing special. I learned more about it by checking the ebay products.

Reflectix has foil on both sides of bubble wrap. Another variation is a flexible but stiff foam on both sides of a foil liner. This product is designed for under hydronic heated floors. Its tough enough to walk on without damaging it. You can tape the hydronic piping right on it and pour cement on top. The information about this sub slab product says that regular foam board will gradually reach the temperature of the ground under it. At this point the hydronic system will labor to the raise the slab temperature and the foam. The foil lined product isolates the two.

 

i have heard that the foil is more effective in keeping a house cool in summer than it is keeping a house warm in winter - don't quite understand that - seems like it should be equally efficient reflecting in either direction - haven't tried it yet tho

 

oops - forgot - DON't make a mistake with vapor barrier - in a few years you might have MAJOR problems

 

Think in terms of a reversal of thermal mass. Instead of absorbing heat energy the foil-like material resists heat transfer. Now this is only to a degree and eventually enough heat or lack there of will radiate through.
Like cooking in the oven and covering something with aluminum foil.
When used in roof insulation and combined with a quality thermal barrier you would have one hell of an insulated roof! The thermal barrier will hold air and slow loss in the typical form while the foil will reflect heat energy both back in your home in winter and back out your roof in summer. It's more effective in summer because of the heat intensity from the sun on your roof. You have to remember science, there is no such thing as cold, just the lack of heat!! Foils work to reflect heat, well the less heat you have then the less they will reflect. In simple terms if its 20 outside and 68 in your house the foil will work to reflect the home's heat in upon itself but can do little about the outside temp because it is lower then the inside temp. Anyhow you could say it shines in hot sunny climates

 

We put this in a house several years ago. We figured up that the savings on electricity (total elec house) would take about 20 years to recoup the cost of the radiant barrier. Obviously, we thought we would save a whole lot more.

 

I use this stuff all the time i believe that it is called insultarp i'll look and post back it is not like the bubble wrap stuff this has a dense closed cell ruber foam between the foil.They also make a product called slab shield made for in floor heating set up's it has foam on the outsides with a foil in the middle,reason for the foil in the middle is the concrete will eat the foil.

 

I have never used it before, but some construction guys I talked to once related that the unfinished house frame-shells in which the radiant barrier had been installed under the roof sheathing were the ones they ate lunch in during the summer, because they were always substantially cooler than outside and way cooler than the as-yet-to-be-gotten-to house shells on the development plot, which were often hotter than being outside due to a lack of a breeze to keep the heat from building up inside.

 

I tried to post on this thread last night but was told it was not accepting any new posts so will try again. This will be shorter than the other one but if you have any questions let me know. I also must say I have not used it yet but plan to in the rabbitry later this year. A catalog I have has a lot of this for sale and different types it is FarmTek you can get a copy from FarmTek.com look in the section for tekfoil. If it works even half as well as they describe it I think it might just be worth using it.

 

I've been looking for a small scrap of the stuff to make a better tinfoil hat, I think the aliens have figured out how to control my thoughts through the regular tinfoil. I gotta stay one step ahead of them if I dont want to go on another killing spree.
Kirk

 

The companies sure put out good product brochures and make the product sound wonderful.

What you need to read before purchasing any is the installation instructions. I really needs an air gap on each side of it for full benefit. At least the kind I bought required it for maximum benefit.

Stick your hand into a mitt made of it and you can sure feel the difference shortly.

 

iv used it for years,i use it for garding in fall and spring.i put it everywhere i heat or cool. also comes w/white plastic on one side for up against block walls or ground. i can save you money over hp but shipping. pm me. nfp

 

unregistered: say what????? what is hp and nfp??? how would someone pm you??

 

My experience was unorthodox, but convinces me this stuff is great. I had part of a roll given to me for free. Last summer was my first in this *old* mobile home, which is loaded with windows. There is not one tree here for shade, but since I'm on a hill there's always a breeze. On a whim, I put this stuff in some of the windows. Looked pretty stupid, but it kept the temps much, much cooler than if I'd let the sun shine in all those windows. It worked like heavy drapes, only better. I'm going to buy a roll this summer for the rest of the windows and inside the roof of the new goat shed.